/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

typedef void TCB_t;
extern volatile TCB_t * volatile pxCurrentTCB;
extern void vTaskSwitchContext( void );

/*
 * Saves the stack pointer for one task into its TCB, calls
 * vTaskSwitchContext() to update the TCB being used, then restores the stack
 * from the new TCB read to run the task.
 */
void portSWITCH_CONTEXT( void );

/*
 * Load the stack pointer from the TCB of the task which is going to be first
 * to execute.  Then force an IRET so the registers and IP are popped off the
 * stack.
 */
void portFIRST_CONTEXT( void );

#define portSWITCH_CONTEXT()                                                              \
    asm { mov ax, seg pxCurrentTCB }                                                      \
    asm { mov ds, ax }                                                                    \
    asm { les bx, pxCurrentTCB } /* Save the stack pointer into the TCB. */               \
    asm { mov es : 0x2[ bx ], ss }                                                        \
    asm { mov es:[ bx ], sp }                                                                      \
    asm { call far ptr vTaskSwitchContext } /* Perform the switch. */                     \
    asm { mov ax, seg pxCurrentTCB }        /* Restore the stack pointer from the TCB. */ \
    asm { mov ds, ax }                                                                    \
    asm { les bx, dword ptr pxCurrentTCB }                                                \
    asm { mov ss, es:[ bx + 2 ] }                                                                      \
    asm { mov sp, es:[ bx ] }

#define portFIRST_CONTEXT()                \
    asm { mov ax, seg pxCurrentTCB }       \
    asm { mov ds, ax }                     \
    asm { les bx, dword ptr pxCurrentTCB } \
    asm { mov ss, es:[ bx + 2 ] }                       \
    asm { mov sp, es:[ bx ] }                           \
    asm { pop bp }                         \
    asm { pop di }                         \
    asm { pop si }                         \
    asm { pop ds }                         \
    asm { pop es }                         \
    asm { pop dx }                         \
    asm { pop cx }                         \
    asm { pop bx }                         \
    asm { pop ax }                         \
    asm { iret }
